1. Field of the Invention
The present invention relates to a thin film magnetic device having a thin film coil and a magnetic film, and relates to a method of manufacturing the same.
2. Description of the Related Art
In the field of electronic devices for various use, a thin film magnetic device such as a thin film inductor or thin film transformer including a thin film coil and a magnetic film has been widely used so far as an integrated passive component.
FIGS. 30A and 30B show an example of a conventional thin film magnetic device (thin film inductor 101) in the related art formed by a rectangular spiral coil. FIG. 30A shows a configuration in plan view of the device, and FIG. 30B shows a configuration in cross section thereof taken along a line V-V of FIG. 30A. The thin film inductor 101 has a stack structure in which a lower magnetic film 104A having an opening 105A in its central portion, an insulating film 102, a rectangular spiral coil 103 having terminals 103T1 and 103T2, and an upper magnetic film 104B having an opening 105B in its central portion are stacked in this order on a substrate 100 in the Z axis direction. In the lower magnetic film 104A and the upper magnetic film 104B, a predetermined magnetic field is applied thereto in the X axis direction during film formation or the like, thereby a magnetization easy axis Me is formed in the application direction of the magnetic field (X axis direction), and a magnetization hard axis Mh is formed in a direction (Y axis direction) orthogonal to the magnetization easy axis, consequently the magnetic films have uniaxial anisotropy.
In recent years, such a thin film magnetic device is expected to be used in a high frequency band such as the GHz (gigahertz) band and the like. Accordingly, a magnetic film having excellent high frequency characteristics, specifically a magnetic film having high magnetic permeability in a high frequency range is desired.
For example, in a thin film magnetic device of the related art as shown in FIGS. 30A and 30B, since the thin film coil is a rectangular spiral coil, a coil part extending in the X axis direction and a coil part extending in the Y axis direction exist respectively, and consequently a coil portion extending along the magnetization easy axis Me and a coil portion extending along the magnetization hard axis Mh mixedly exist. Therefore, in a coil part in which the magnetization direction generated by the coil is orthogonal to the magnetization easy axis Me (X axis direction), while magnetic permeability is naturally low in a low frequency range, certain magnetic permeability can be kept in a high frequency range. On the other hand, in a coil part in which the magnetization direction is parallel to the magnetization easy axis Me (Y axis direction), while magnetic permeability is high in the low frequency range, the magnetic permeability is abruptly decreased in the high frequency range. Hence, use efficiency of magnetic characteristics of the magnetic film is low (in the case of a square spiral coil, about 50%), and consequently high magnetic permeability has been hardly exhibited in the high frequency range.
Thus, to improve the magnetic permeability in the high frequency range, thin film magnetic devices have been proposed as shown in Japanese Unexamined Patent Application Publication (JP-A) Nos. H8-172015, 2001-143929, and H11-87125. Among them, JP-A No. H8-172015 discloses a device in which a direction of the magnetization easy axis of a magnetic film is varied by using magnetic shape anisotropy of the magnetic film in correspondence to a coil part in each of two directions of a rectangular spiral coil. Specifically, a magnetic film is separately formed in a magnetic field in correspondence to the coil part in each of two directions, so that both of the coil parts in two directions are orthogonal to the magnetization easy axis to improve magnetic permeability in the high frequency range.
JP-A No. 2001-143929 discloses a device in which the magnetization easy axis direction of a magnetic film is rotated by forming fine slits circulating in correspondence to coil parts of a rectangular spiral coil. The device is designed to improve magnetic permeability in a high frequency range by making both of the coil parts in two directions to be orthogonal to the magnetization easy axis as in the JP-A No. H8-172015.